When comparing Qubicle vs Paint3D, the Slant community recommends Qubicle for most people. In the question“What are the best voxel editors?”Qubicle is ranked 2nd while Paint3D is ranked 5th. The most important reason people chose Qubicle is:

Clean user-interface. Includes features such as hue and saturation, mirror, fill, hollow, etc.

Ranked in these QuestionsQuestion Ranking

Pros

Pro

Easy to use

Clean user-interface. Includes features such as hue and saturation, mirror, fill, hollow, etc.

Pro

Allows working with multiple model matrixes in a single window

Pro

A lot of professionals use it

Pro

Has a free version

There's a limited free version of the editor available.

Pro

Affordable

Has a free trial version and a cheap full version.

Pro

Scripting support

Can be used to generate models, import stuff, animate, etc.

Pro

Can export traditional 3D models

Pro

Interoperates with 2D paint programs

Pro

Supports multiple voxel formats

Pro

Easy to use

Pro

Uses 32-bit color with real volumetric transparency

Pro

Supports both "per voxel" drawing and smooth "sculpting"

Cons

Con

No perspective camera, only orthographic

It can be confusing editing models sometimes because the camera is an orthographic one: you can't view things with a perspective camera.

Con

Free version is highly limited

Free version of the editor is highly limited. It lacks import/export options and certain modifiers.

Con

Missing Linux support

Con

Requires OpenGL support

If your computer doesn't support OpenGL 3.0, it won't open.

Con

2.0 update made the interface a bit less functional

The 2.0 update of Qubicle increased the buttons of the interface. effectively removing some of the functionality that was easily accessible before from easy reach. Now you have to pick and choose what is readily available on the main menu.

Con

The web site's domain is no longer available

Using the WayBackMachine to get the site's contact email address, I attempted to contact the developer to find out what the story is. There has been no response. The WayBackMachine's last archive date for the site was 11Jan2016. Their cached version of the paint3D.net's forum does not have any post explaining what happened.